and Weather water
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Energy balance requires energy transport
Energy transport
Ingreadients to make weather
1. 2. 3. 4. 5. 6. 7. Heating at poles, cooling at higher latitude This causes pressure gradient to form Pressure force balances Coriolis force (i.e., geostrophic) to make winds westerly (so no energy is moved poleward past the edge of the Hadley cell!) Temperature continues to build in the tropics, making the pressure force stronger Finally, this can not be balanced by the Coriolis force, and the pile of air collapses (just like a growing pile of homework on piling up on my desk) Since this occurs when the pressure force is stronger than the Coriolis force, we see the spinning in the direction of the pressure force. This is a cyclone! Which must have low pressure.
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Storm tracks?
Hadley cell moves heat (temperature) from equator to subtropics Then we know there is transport of energy as both sensible (temperature) and latent (water) heat from the subtropics to midlatitudes. This is in the region of the Ferrell cell (recall the Ferrell cell is the one that looks like it goes backwards) This is done by storms a.k.a., mid-latitude weather systems a.k.a., cyclones a.k.a., low pressure systems a.k.a., baroclinic cyclones
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Storm tracks
winter spring
summer i.e., location of cyclones fall
http://www.cpc.noaa.gov/ products/precip/CWlink/stormtracks/strack.shtml
Storm strength: how low are the lows? (pressure depth)
December-February
December-February
June-August
June-August
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Final answer
Because of the Coriolis force and geostrophic balance, the wind in the subtropics is expected to be purely westerly. A paradox! No heat can be transported to the polar regions. Explain!?
a) b) c) d) e) The tropics are not in energy balance The ocean is be responsible for heat/energy transport outside of the tropics The tropics must get very cloudy so that the albedo is high and there is a local energy balance There must be some other way that the atmospheric motions can occur in the north/south direction Somebody ships sugar cane (Snickers) from Brazil to the US every day.
Meridional (poleward) energy transport
In the tropics, the overturning circulation moves heat from the equator to the subtropics In the midlatitudes the energy is transport my storms Heat transport is by both temperature and water!
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Water and energy
Recall heat capacity: Put energy in, water heats up:
What happens if it reaches the boiling temperature?
Take energy out, water cools down:
What happens if it reaches freezing temperature?
Heat capacity of ocean water: Heat capacity of air: Temperature
3993 J/kg/K 1005 J/kg/K
Lets see what happens to 1 kg of water
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Three phases of water
Gas Liquid Solid water vapor liquid water/ocean ice/snow/ice sheets
Same stuff, but different configuration of molecules! Requires energy to go from one to the other. Gas Solid molecules locked in place Liquid Molecules slide past one another, but interact Molecules freely fly around, bombing into one another sometimes Higher energy
Lower energy
Phases of water
e.g., snow, hail, ice sheets, sea ice, glaciers e.g., ocean, lakes, rain drops
e.g., atmospheric water vapor
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Latent heat
Energy required to change from liquid to gas (i.e., evaporation of water to water vapour) So when boiling water, heats up to 100 C. Then keep putting in energy (i.e., flame) temperature stays the same, but turns into gas Be warned, dont put hand in steam! (colder hand allows the gas to condense, and all that energy is converted into heat... And lots of it!)
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Consider: 1kg of water warms by 4K How much energy? Hea...